Page 2 of 4: C31885 Rev B 10.03
3.4 EMC
The G123-815 emits radiation well below the level called for in
its CE mark test. Therefore, no special precautions are required
for suppression of emissions. However, immunity from external
interfering radiation is dependent on careful wiring techniques.
The accepted method is to use screened cables for all
connections and to radially terminate the cable screens, in an
appropriate grounded cable gland, at the point of entry into
the industrial steel enclosure. If this is not possible, chassis
ground screw terminals are provided on the G123-815.
Exposed wires should be kept to a minimum length. Connect
the screens at both ends of the cable to chassis ground.
4 Power supply
24V nominal, 22 to 28V
20mA @ 24V without a load, 145mA @ 100mA load.
If an unregulated supply is used, the bottom of the ripple
waveform is not to fall below 22V.
5 Set-up adjustments
5.1 Digital noise filter
This filter removes the digital quantization noise, due to the
PLC update period, in the PLC output signal. Because PLC’s can
have low frequency period noise that the valve can respond to,
it is important to remove this update rate noise so the valve
does not buzz and the load does not follow. The update
period of the PLC needs to be known so the correct filter time
constant can be selected. Initially set the filter period to be
equal to the update rate. Switch values sum, so if you need
15mS, select 10 and 4.7.
When the system is operating, a final check of the time
constant can be made. If the valve buzzes, a greater time
constant is required. If the valve does not buzz, reduce the
time constant until buzzing is detected, then increase it until
the buzzing just stops.
To calculate the 3dB frequency roll off point, use the formula:
f =
159
Hz, where T = the sum of mS period switches selected
T
5.2 Low Rin
The “low Rin” switch drops the input resistance for the PLC
signal from 100k Ohm to 1k Ohm. This can improve the noise
immunity of the signal. Be sure the PLC output can deliver
±10mA that is needed when low Rin is selected.
5.3 Valve drive signal
Select the output signal to match the valve requirement.
If voltage is selected, the ± 10V output can drive up to ±
10mA. If current is selected, the full scale current output will
then need to be selected on the valve current switches. The
switches sum, so if 45mA is required, select 30, 10 and 5mA.
Maximum output current, in current mode, is ± 100mA.
6 Test points and indicators
The Iv and Vv LEDs show the polarization and level of the
selected output signal.
The valve test point gives the actual voltage on the valve
output terminal. When the output signal is selected as current,
a knowledge of the valve’s input resistance is needed to
interpret the test point signal. For instance, if 10mA is selected
and a valve with 200 Ohm input resistance is connected, the
signal on the valve test point will vary between ± 2V.
The probe test point enables a check of the filtered position
transducer signal.
7 Withdrawing the circuit card from
its case
The circuit card needs to be withdrawn from its case to set the
digital noise filter switches, to select the output signal type,
to select the current and to select low Rin.
To do this, push one tab in with a pen or screwdriver, while
gently pulling on the top cover on that side. The cover will
release approximately one mm. Repeat on the other side and
then withdraw the cover and circuit card until the required
switches are exposed. The rigidity of the connecting wires will
hold the circuit card in position while the switches are set.
Cable gland
100mm Loop
Cable
Enclosure
Cable
Wire soldered
to screen
Drain wire.
or
(Heat shrink to
cover the screen)
Alternative Wiring
probe
Iv
valve
Vv
0V
Test point
Test point
Test point
LED
LED
BUFFER AMP
1
2
3
4
5
6
7
8
5
10
20
30
50
mA
V
1
2
3
4
5
0.22
4.7
10
22
Lo Rin
Output
Filter
mS
not in use
Output
V
6
7
8
2.2
S1
S2
